Gateways are what? Gateway types, principle of operation

"Communication" of computers with each other includes many devices, and one of them is a gateway. What is that? What are the types? What is their principle of operation?

What is a gateway

This name has a hardware router, as well as software that is used to connect computer networks. A prerequisite is the ability to use protocols of different types (for example, local or global). The gateway mask is used for recognition. This is a kind of identifier in the global network. It is believed that the gateway is installed, if there is a transfer of useful data from the user's point of view.

What is it like?

The gateway converts protocols of one type to another. A good example is the case where a local computer and the world network connect. Then a network gateway is used. To present a hardware example, I propose to look at something else. A router (router), a very popular and used device, is the same hardware network gateway. They can work with all popular operating systems. The main task performed by the network gateway is the conversion of protocols between different networks. It can receive, process and send packets. Moreover , data transmission can be performed both on one protocol and on several protocols.

Gateways are such subjects of technical systems that can be implemented as a hardware or software solution, or connected together (which is the most common). But usually they are the applications installed on the router and / or the computer. Gateways are devices that all protocols with transmitted data must understand. They should be able to encrypt and decode all information received and sent. Speaking about the shortcomings of gateways, it should be noted that they usually work much slower than conventional routers, switches and network bridges. They can act as a node or an end point of the Internet. Speaking about the latter, it is necessary to distinguish between hosts and gateways. It is very important. So, the first provide Web users with computers web pages, and the latter connect different networks. The latter includes the server, which controls the traffic when data is exchanged between the company's computers and the Internet. For large volumes, the gateway is usually integrated with a firewall and a proxy point. To manage the distribution and conversion of packets, it combines with the router. If we talk about software, then it can be installed both on the server and on the computer.

Gateway functions

It establishes routes for sending data packets to various heterogeneous network interfaces. Also, it can localize all processed traffic. There may be a subnet gateway, or a data link. There is also a specific function, which has not yet become widespread. Now talk about the voice gateway. It is necessary to transmit sound traffic. The voice gateway is used in phones.

Principle of operation

How's it going? Gateways are devices that can work on all popular operating systems. We will look at the data path of the moment when the user pressed the "Send" button. First, an explanation is made using machine languages, which the computer requires. Then all information is encoded in binary code. It is divided into data packets. Each of them contains information, part of what it is and where it needs. The encryption is performed. The route is then determined, and the data packets are sent to the recipient. When they arrive at the destination, then the above processes occur in reverse order, except that decryption is performed. That is, this device works as a gateway-router. Now let's look at the types of gateways that exist.

Default gateway

In protocols, this is the name of the address where all traffic is sent, for which it is impossible to route. For this property it is also called the gateway of last hope. To determine where the data is to be sent, a special routing table is used. If you can not determine the ultimate goal, then they are transferred to it. The use of gateways of last hope found in networks where the central routers are well expressed, in their client segments, and also just small in size. In the table it is given by such record: "network 0.0.0.0 with mask 0.0.0.0". Configuring the gateway of this - it's not complicated (usually it is configured when installing the drivers).

Call gateway

Looking ahead, I will inform you that it is not used in IDT. A characteristic feature of this gateway is that it has a WC field. Therefore, it is possible to immediately transfer 2 ⁵ = 32 words to a procedure that is called through the stack.

Task Gateway

Its important advantage is universality - it can work in all three descriptor tables. But the displacement fields are not used here, so they can take any value. Also as a segment, TSS has found application here. Configuring the gateway, despite its versatility, is not the easiest thing to do.

Interrupt Gateway

It is used exclusively in IDT. It can reset the IF interrupt flag when entering the processing routine. Since the previous value of the register is always stored on the stack, when it exits from the task being performed, it assumes the initial position. An important advantage is that this gateway can handle part of the interrupts that occur in CLI mode.

Gateway trap

It is also used exclusively in IDT. At the same time, he was given the title of the simplest gateway. So, when interrupts arrive, it goes to the processing procedure. If necessary, you can even switch the stack. Let's consider in detail one of the samples presented in the article.

Additional options for using default gateways

In general, what are they, and what role is played in data transmission? Above, only one possibility was outlined, but it does not give a full idea of what and how. So, the default gateway allows you to simplify the coordination of traffic. How? To do this, it sends all the received data to the central routers, which can see a more "voluminous" picture, and accordingly - they have a better chance of finding the recipient. Also it is necessary to consider, from what the table of routing of workstation is made. So, it has loops, a local network segment and the default gateway itself. The role of the latter is to receive all the traffic that the first two recipients did not understand. When multiple devices or units of equipment are connected to the same router, the default gateway is the only available form of addressing addresses for data. When using multiple connections, this form of data exchange loses its value. In this case, it is not necessary to configure the gateway for the default.

Why does he have such a name

How did it happen? It should be noted that the application varies depending on the sphere, although there is no difference in the functional. The term "gateway for default" is used on workstations. Its use in these cases is the standard mode of operation of this unit of equipment. The term "last hope gateway" is applied to routers, where the occurrence of such a situation is considered not normal, since this device should always know where to deliver the information packets.

Conclusion

Summarizing, we can say that the topic of locks is extremely capacious. If you undertake to describe in detail what and how in relation to them, then even the smallest text will exceed the size of this article. But such a detailed level of presentation still does not need simple users and even those who set them up. This information can only be used if the person himself wants to develop such a device, but here the material must be written for a whole book.